1. Field of Invention
The present invention relates to improved bolted-on automotive exhaust manifold gasket assemblies for internal combustion engines, and more particularly to such gaskets having improved heat insulating characteristics as compared to commonly known prior art exhaust manifold gaskets.
2. Description of the Prior Art
Those skilled in the art will appreciate the difficulty of maintaining a high quality seal between the cylinder head exhaust port of an internal combustion engine and the exhaust manifold normally secured thereto via flange. Typically, an exhaust manifold gasket interfaces with, i.e. is affixed between, the cylinder head exhaust port of the engine and the engine exhaust manifold, indeed one of the hottest areas of an exterior engine environment. As a result of widely varying thermal cycles and significant vibration, an exhaust gasket is subject to rapid deterioration if its design is inferior.
One means of enhancing longevity of such gaskets in recent years has been to bracket together the exhaust manifold gasket with an insulating sleeve installed into the cylinder head exhaust port for reducing thermal stresses on both the cylinder head port and the exhaust gasket body. The associated structure, however, has been formed in several pieces, and is thus relatively cumbersome to install on the assembly line, in addition to being costly as result of the necessity of manufacturing extra parts. A consolidation of parts would be an attractive solution to resolve the issue.
The present invention is an improved exhaust manifold gasket for sealing between a cylinder head exhaust port and a flanged exhaust manifold of an internal combustion engine. In a preferred form, the exhaust manifold gasket of this invention contains an integral heat-insulating sleeve for reducing thermal stresses on cylinder head port and gasket body. The gasket is comprised of first and second metal layers fixedly secured together along a unitary plane. The gasket includes one medially positioned aperture for the passage of high-temperature exhaust gases, wherein the first and second layers define at least one full sealing bead disposed about the circumference of the aperture. Bolthole apertures are spaced radially outwardly of the exhaust gas aperture, and the second layer includes a plurality of circumferentially disposed leg portions symmetrically disposed about the exhaust aperture. The leg portions are positioned orthogonally to the unitary plane, and adapted to receive the attached sleeve designed to extend into the exhaust port. The sleeve is laterally positioned so as to form an air gap between its exterior circumference and the interior circumference of the exhaust port.